We report that wide field-of-view (FOV) optical coherence tomography images with high lateral resolution can be obtained by using superresolution and 3D image stitching techniques. About 3 times lateral resolution improvement from 6.20 μm to 2.19 μm using a focusing lens of 0.08 numerical aperture has been demonstrated. With such lens the FOV is generally small owing to off-axis focusing degradation. To enlarge the FOV while maintaining high lateral resolution, 3D image stitching technique is introduced to effectively reconstruct an ultra-wide FOV 3D image of 2.10x1.15 mm2 lateral area from ten C-scans of 500×500 μm2 FOV. Improved FOV with high lateral resolution should benefit various biomedical imaging applications.

We introduced a laser-based noncontact shallow water depth measurement technique from a flying unmanned aerial vehicle (UAV). The water depth is measured by imaging two laser beam spots scattered from the surface and bottom of the water. The effect of water surface waves and UAV tilt angles to the depth measurement has been studied for practical applications. We have further developed this laser-based detection system consisting of a green laser, a global positioning system, a camera with a narrow field of view lens, a laser range finder, and a single-board computer. The measurement system onboard of a UAV flying over a small lake has demonstrated satisfactory water depth measurement capability. The low-cost light weight UAV-based water depth measurement should benefit water depth monitoring, mapping, and reporting in a hazardous environment offering flexibility, mobility, and remote control safe operation.

Planar concave grating wavelength demultiplexers with a flattened spectral response are realized based on SU-8 polymer waveguides. The flattened spectral response is accomplished by using an optimized multimode interference (MMI) coupler as the input aperture of the planar waveguide for all spectrally separated channels. The mode field distribution at the input of the planar waveguide is controlled by adjusting the width of the input taper connected to the MMI coupler. The devices are fabricated by cost-effective one-step UV lithography. Experimental results show that the desired flattened spectral response has been realized. The on-chip loss, crosstalk, and nonuniformity of the fabricated device are −14.8, −22, and 2.5 dB, respectively.

A 4-channel planar concave grating device with a flattened spectral response based on SU-8 polymer is presented.
The flattened spectral response is accomplished by using an optimized multi-mode interference coupler as the input
aperture of the device for spectrally separated channels. The mode field distribution in the input plane is controlled
by adjusting the width of input taper coupled to the multi-mode interference coupler. The effects of the input taper
width on the flattened spectral response are demonstrated in detail through simulation results. The devices are
realized by using an SU-8 polymer strip waveguide with a UV lithography technology. Experimental results show
that the flattened spectral response can be easily controlled by adjusting the taper width.

Polymeric waveguides with tunable optofluidic couplers are fabricated by the vacuum assisted microfluidic technique for card-to-backplane optical interconnect applications. The optofluidic coupler on a backplane consists of polymer waveguides and a perpendicular microfluidic channel with inclined sidewalls. An index matching liquid and air bubbles are located in the microfluidic hollow channel. The activation or deactivation of the surface normal coupling of the optofluidic coupler is accomplished by setting air bubbles or index matching liquid to be in contact with the waveguide mirrors. 10 Gbps eye diagrams of the card-to-backplane optical interconnect link have been demonstrated showing the high performance of the interconnect system.

We report an integrated optical coherence tomography (OCT) and reflectometry system for ophthalmology imaging. The dual-functional device provides a complementary high-resolution tear film evaluation by reflectometry and anterior segment imaging by OCT, offering a more comprehensive anterior segment examination. The imaging measurement capabilities have been demonstrated on a human eye as well as on a model eye. The minimum measured tear film thickness is 0.3 μm with measurement resolution of less than ±0.58% of film thickness yet the OCT anterior segment offers a depth resolution of 7 μm with a 45-nm bandwidth superluminescent light source at 840-nm center wavelength. The integrated system has demonstrated the capability for three-dimensional imaging in the anterior segment of the eye.

We report on the fabrication of a light sensitive waveguide via vacuum assisted microfluidic (VAM) soft
lithographic technique. UV curable light insensitive waveguides function like typical polymer waveguides with
desired mode confinements while the light sensitive waveguides formed by an azobenzene based polymer resin can
achieve refractive index modulation through green or blue laser illumination. The refractive index modulation is
instant and reversible in the light sensitive waveguide. The VAM technique is used for the fabrication of multisection
waveguides using different resins at the same time which is unique compared to conventional single material
waveguide fabrication. The effective fabrication of various waveguide sections with the light sensitive azobenzene
based UV curable resin can result in many functional waveguide devices for photonics applications.

Polymeric waveguides with dynamic coupler array are fabricated by vacuum assisted microfluidic technique for
card-to-backplane optical interconnect applications. The dynamic optical coupler on backplane consists of 45°
integrated waveguide mirrors and a perpendicular microfluidic channel for flow motion of index matching liquid
and air bubbles. Controlled positioning of the air bubble or index matching liquid in contact with the integrated
mirror can effectively turn on or off each surface normal waveguide coupler for card-to-backplane optical
interconnection. The size of the integrated mirror determines the coupler efficiency. Effective surface normal optical
coupling is demonstrated.

We demonstrate that a 2D eight-fold photonic quasi-crystal (PQC) can be produced by a specially designed prism
via single-exposure holographic lithography. Compared with traditional eight beams in half space for eight-fold
quasi-crystal, we only use 5 beams in ¼ space. From group theory and computer simulation, we have verified the
feasibility of the particular configuration and observed the simulated patterns. Experimental results observed under
SEM agree well with the expectation, confirming that the specially designed prism can be used to fabricate eight-fold
photonic quasi-crystal. This prism-assisted holographic lithography using less exposure beams may benefit
mass production of complex quasi-structures.

We report on the fabrication of an eight-channel single-mode waveguide array via vacuum assisted microfluidic soft
lithographic technique. The incorporation of sectional flow tapers perpendicular to the waveguide direction allows
for the realization of long single-mode channel waveguide arrays, thus overcoming the waveguide length limitation
set by the viscosity of the UV curable resin. The refractive index and other properties of the synthesized UV curable
core waveguide resin can be tuned through the reformulation of material composition.

Three-dimensional (3D) microstructures are fabricated by prism-assisted inclined ultraviolet (UV) lithography. The
exposure angles of slanted structures ranging from 0° to 65° in SU-8 photoresist can be easily achieved without
immersion in index matching liquid. The sample surface reflection of UV light can be utilized for the fabrication of
symmetric structures. Tripod structures have been fabricated by one-step UV exposure with corner prism. Examples
of various achievable 3D microstructures are presented.

Silicon photonics can found applications in optical interconnects and optical signal processing. Recent years, silicon
photonics was developed rapidly. In this paper, we report our research work on silicon photonics. Based on the standard
CMOS foundry, we studied the silicon waveguides and related photonic components.

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